Radiation therapy is often used in the medical industry as treatment for tumors. Radiation therapy is the process of using high energy x-rays or other energy sources to kill cancer cells and to shrink tumors.
In radiation treatment, the radiation beam may be wide with low intensity, resulting in large areas beyond the tumor being exposed to the radiation, or narrowly focused on the tumor with high intensity. For high intensity radiation treatment, the radiation beam is narrowly focused onto the tumor in order to minimize risks to healthy cells. The intensity of the radiation may vary depending on the type and size of the tumor. Therefore, in order to control the patient's dosage, it is necessary to control the beam's intensity, shape, and uniformity.
Generally, radiation therapy includes multiple treatments over a period of time. In order to maintain control over the dosage, quality assurance tests are performed before each treatment. Because each patient receives multiple treatments over a period of time and each treatment requires a quality assurance test to be performed on the radiation beam prior to exposing the tumor to the radiation, there is a need to maintain repeatability between treatments for each individual patient.
Radiation quality assurance tests are performed in the same environment that patients are treated, on patient positioning systems that includes a radiation-transparent board such as Halcyon™ patient positioning systems. Typically, quality assurance tests have been performed by positioning an x-ray detection device, such as the Thebes® and the Double Check Pro® x-ray detection devices sold by Fluke, Inc., into a bracket that is placed at any location onto the board. The table is then moved so that the x-ray detection device is aligned with the beam. At this location the shape, uniformity, and intensity of the beam is calibrated using the x-ray detection device.
Once the beam has been calibrated, the x-ray detection device is removed from the table. The patient is then placed on the table, and an attempt is made to position the patient so that the tumor is at the same location on the table at which the x-ray detection device was positioned. However, in order to align the x-ray beam to the tumor, it is necessary to determine the location of the calibration point. Unfortunately, insofar as the x-ray detection device is removed from the table when the patient is placed on the table, it can be difficult to position the patient so the tumor is at the proper location. Furthermore, because the x-ray detection device may be placed at different locations on the board for each calibration, the coordinates of the tumor relative to the calibration point must be calculated during each visit for the same patient. Therefore, it is difficult to ensure repeatability for recurring treatments of each individual patient. Also, the need to recalculate the coordinates of the tumor relative to the calibration point significantly slows the quality assurance process procedures. In addition, there may be less dosage consistency from treatment to treatment because the manual process of recalculating the coordinates of the tumor relative to the calibration point at each visit may result in errors.
Therefore, there is a need for a quality assurance system and process that is repeatable for each patient on recurring treatments in order to speed up the process and increase the accuracy of radiation treatments.